Combinatorial molecular layer epitaxy device

ABSTRACT

A combinatorial molecular layer epitaxy apparatus is provided which includes a common chamber ( 22 ) having pressure therein controllable; one or more conveyable substrate heating units ( 36 ) having a substrate holder ( 48 ) for holding one or more substrates in the common chamber; and one or more process conducting chambers ( 24, 26, 28 ) having pressure therein controllable and provided to correspond to the substrate heating units. The process conducting chambers includes a growth chamber ( 24 ) which has a multiple raw material supply means for supplying raw materials onto a substrate ( 5 ) held by a substrate heating unit, a gas supply means for feeding a gas onto a surface of the substrate, and an instantaneous observation means for instantaneously observing epitaxial growth of monomolecular layers for each of the layers on the substrate surface, thereby rendering the formation of vacuum chambers constituting from substrate heating unit and process conducting chambers, which are controllable in temperatures and pressures.

TECHNICAL FIELD

This invention relates to a combinatorial molecular layer epitaxyapparatus that is useful to form an inorganic superstructure, a metallicsuperstructure or an organic superstructure, especially to make anefficient search for substances in a short period of time.

The invention further relates to a combinatorial molecular layer epitaxyapparatus that permits a substrate or substrates to be conveyed in theapparatus as a thin film forming system and, to be conveyed in a statein which they remain heated, and successive processing chambers to beformed as independent vacuum chambers with pressure and temperaturestherein controllable independently of one chamber from another.

BACKGROUND ART

At recent times, following the discovery oflanthanum/barium/copper-oxide superconductive materials, a greatprogress has been made of thin film forming technologies for hightemperature superconducting oxides. With such a progress, efforts havebeen expended extensively to search for and to investigate a variety ofnew functional substances for metallic, inorganic and organic materials.

In the field of forming thin films of high temperature superconductingoxides, the fact that a functional oxide material such as of perovskitetype is itself a multicomponent material with a plurality of oxidesmakes it difficult to theoretically predict an optimized componentproportion and a correlation between thin film preparing conditions andresultant properties, and provides no alternative but to adopt a trialand error approach for optimization.

Under the circumstances, X. -D. Xiang et al conducted a search for oxidehigh temperature super-conductors on combining a multi-sputtering thinfilm forming process with a mask patterning technique of coveringparticular areas on a substrate with masks, and effecting acombinatorial synthesis of inorganic materials in which a number ofinorganic substances are synthesized parallel to each other, and showedthat this approach had a power in functional search for a multicomponentmaterial (X. -D. Xiang et al, Science, 268, 1738 (1995)).

Also, G. Briceno et al in search for colossal magnetoresistance (CMR)materials, prepared from a new material: LnXMYCoO_(3−δ)(Ln=La, Y; M=Ba,Sr, Ca, Pb) with cobalt oxide as its base component, 128 specimens withvaried compositions sputter-evaporated using combinatorial synthesis andthereafter sintered in an oxygen atmosphere. And based on themeasurement of magnetic resistance of those specimens, they revealedthat even a multi-oxide material exhibited a maximum magnetic resistanceratio 72% CMR. Significantly, discovery and optimization of a newCoO₂-based CMR material were achieved on conducting a combinatorialsynthesis only twice with varied sintering conditions.

It can be seen, however, that a combinatorial synthesis referred toabove for inorganic materials in which forming thin films are effectedat a room temperature in either case only plays a role of simplycontrolling compositions. Also, no combinatorial synthesis has become areality of thin films with a superstructure formed by epitaxial growthfor each of molecular layers of materials either organic or inorganic.

On the other hand, it is noted that in a conventional thin filmmanufacturing system which involves a plurality of processing stages,wafers have been conveyed between different process stages by man or arobot, pressure and temperature process parameters have been set up forthe individual processing stages one after another.

Especially where a wafer is required to have a clean surface, wafersmust be conveyed through a conveying path that is hermetically sealed ina clean space.

Since such a conveyer is normally not adapted for high temperaturewafers, however, it has been common to rely on a time consumingprocedure in which hot wafers processed in a given process stage iscooled to a room temperature and then conveyed into a next process stagewhere they are heated to a required temperature for processing.

Further, the need to set up process parameters such as a reactionpressure and a wafer temperature one after another for the successiveprocessing stages individually makes it unsuitable to process waferscontinuously in different process stages.

Accordingly, the present invention is provided to resolve such problemsmet in the prior art as described, and has for its first object toprovide a combinatorial molecular layer epitaxy apparatus that permitsmolecular layers to be formed each individually by epitaxial growth toform an inorganic, metallic or organic superstructure of such molecularlayers, and that allows an efficient search for a substance to beconducted in a short period of time.

Another object of the present invention resides in providing acombinatorial molecular layer epitaxy apparatus that is capable ofconveying wafers in their heated state, and permits successiveprocessing chambers to be formed as independent vacuum chambers withpressure and temperatures therein controllable independently of onechamber from another.

DISCLOSURE OF THE INVENTION

In order to achieve the first object mentioned above, the presentinvention provides a combinatorial molecular layer epitaxy apparatusthat comprises a common chamber having pressure therein controllable;one or more conveyable substrate heating units having a substrate holderfor holding one or more substrates in the common chamber; and one ormore process conducting chambers having pressure therein controllableand provided to correspond to the substrate heating units, the saidprocess conducting chambers including a growth chamber which has amultiple raw material supply means for supplying raw materials onto asaid substrate held by a said substrate heating unit, a gas supply meansfor feeding a gas onto a surface of the substrate, and an instantaneousobservation means for instantaneously observing epitaxial growth ofmonomolecular layer for each of the layers on the substrate surface,thereby permitting growth temperature, pressure and supply of the rawmaterials to be controlled for each of the substrates and producing agroup of substances caused each to grow epitaxially in an individualmonomolecular layer and brought together in a single series of reactionsfor each of the substrates, systematically in accordance withindications of the instantaneous observation means.

The construction described above permits [multiple rawmaterials]×[multiple substrates]×[reaction parameters such astemperature, pressure and flux (rate of build-up) from gas phase] to beselected or controlled independently of one another and put together inany desired combination, and hence is capable of synthesizing orbringing together in a single series of reactions a group of substancesinto an epitaxial growth superlattice structure systematicallycontrolled.

Also, in a combinatorial molecular layer epitaxial growth apparatusaccording to the present invention, the multiple raw material supplymeans preferably includes a laser molecular beam epitaxy means forvaporizing with an excimer laser beam a plurality of targets ofdifferent solid raw materials and for forming a thin film of acomposition as aimed on each of the substrates.

This construction permits a limited depth of surface of a target to bemomentarily vaporized and gasified and a thin film of a composition asaimed to be formed. It is possible to form a thin film, e. g., of aninorganic superstructure.

Also, in a combinatorial molecular layer epitaxial growth apparatusaccording to the present invention, the multiple raw material supplymeans may preferably include a laser molecular beam epitaxy means and asaid substrates is composed of a material selected from the group whichconsists of α-Al₂O₃, YSZ, MgO, SrTiO₃, LaAlO₃, NdGaO₃, YAlO₃, LaSrGaO₄,NdAlO₃, Y₂O₅, SrLaAlO₄, CaNdAlO₄, Si and compound semiconductors.Further, the target solid raw materials may include substances adaptedto form a material selected from the group which consists of a hightemperature superconductor, a luminescent material, a dielectricmaterial, a ferroelectric material, a colossal magnetoresistancematerial and an oxide material.

This construction permits a target raw material to be consistentlysupplied to a substrate surface and makes the probability of adherencealmost 1 regardless of a particular component. These featuresadvantageously act in forming on a substrate a thin layer ofmonomolecular layers each individually caused to grow by epitaxialgrowth, of a high temperature superconductor, a luminescent material, adielectric material, a ferroelectric material, or a colossalmagnetoresistance material.

Further, in a combinatorial molecular layer epitaxy apparatus accordingto the present invention, the multiple raw material supply means maypreferably include a target turn table supported to be rotatable andvertically movable for carrying targets, and a masking plate meansdisposed between said targets and said substrates and supported to berotatable and vertically movable. Also, the masking plate means maypreferably comprise a plurality of masking plates having differentmasking configurations which are exchangeable in succession whileepitaxial growths are effected. Further, the masking plate means maycomprise a mask movable horizontally with respect to said substrates andadapted to cover and uncover either or both of a said substrate and agiven area thereof with said movable mask.

This construction with the aid of a movable mask caused to move toprovide the mask plate means with masking patterns permits asuperlattice thin films varied in composition or laminated structure tobe prepared in a plurality of given areas of a substrate.

Also, in a combinatorial molecular layer epitaxy apparatus according tothe present invention, the multiple raw material supply means maypreferably comprise a laser molecular beam epitaxy means, and theinstantaneous observation means may then comprise a reflex high-energyelectron beam diffraction analysis means.

This construction permits providing a thin-filmed, for example, highmelting point and multi-component oxide material while monitoringformation of layers each individually on epitaxial growth.

Further, a combinatorial molecular layer epitaxy apparatus according tothe present invention may preferably further include a target loadinglock chamber for loading targets with materials therein.

This construction permits exchanging targets in their clean statewithout exposing them to an environmental atmosphere.

Also, in a combinatorial molecular layer epitaxy apparatus according tothe present invention, the multiple raw material supply means maypreferably comprise a gas source molecular beam epitaxy means adapted toapply and thereby to supply a flow controlled stream of a gaseousorganometallic compound through a nozzle means onto each of thesubstrates.

This construction permits forming, e. g., a metallic or organicstructure by using a gaseous material such as of an organometalliccompound.

Further, in a combinatorial molecular layer epitaxy apparatus accordingto the present invention, the multiple raw material supply means maypreferably comprise a gas source molecular beam epitaxy means, and theinstantaneous observation means may then comprise an optical means thatmakes observation based on any of reflectance differentialspectroscopic, surface light absorbing and surface light interferometricprocesses.

This construction permits effecting an epitaxial thin film growthformation of a metallic or organic structure while monitoringmonomolecular layers for each individual layer in growth.

Also, in a combinatorial molecular layer epitaxy apparatus according tothe present invention, the substrates may preferably be substratescomposed of Si or a compound semiconductor.

This construction permits forming a metallic or organic superlatticestructure of monomolecular layers each individually caused to growepitaxially, on Si and compound semiconductor made substrates.

Further, in a combinatorial molecular layer epitaxy apparatus accordingto the present invention, the substrates may preferably comprisesubstrates whose surfaces are made flat on an atomic level and whoseoutermost atomic layer is identified.

This construction provides the ability to observe RHEED oscillationsthat, for example, last with an extra-regularity and for a prolongedperiod of time, and thus permits ensuring epitaxial growth to proceedfor each individual monomolecular layer

Also, in a combinatorial molecular layer epitaxy apparatus according tothe present invention, the common chamber may preferably be providedwith a substrate holder loading lock chamber for exchanging thesubstrate holders in a state in which a high vacuum is held therefor.

This construction permits exchanging substrates in their clean statewithout exposing them to an environmental atmosphere.

Further, in order to achieve the second object mentioned above, acombinatorial molecular layer epitaxy apparatus according to the presentinvention has a said substrate heating unit adapted for a pressurecontact with a said process conducting chamber to vacuum seal the same,the substrate heating unit and process conducting chamber then togetherforming an independently pressure controllable vacuum chamber.

This construction permits substrates to be transferred between theprocess conducting chambers in their heated state and makes the vacuumchambers pressure and temperature controllable independently of one fromanother.

Also, in a combinatorial molecular layer epitaxy apparatus according tothe present invention, the substrate heating units may preferably bejointly adapted to be turned around and vertically moved by a carrierplate so as to be conveyed into association with said process conductingchambers in succession.

This construction permits the substrate heating units to move and turnalong a given path or orbit and each to be transferred into associationwith a given process conducting chamber, and allows a substrate holderloaded with a number of substrates to be transferred into the processconducting chamber. It thus permits a plurality of process conductingchambers to conduct the processes in parallel.

Further, a combinatorial molecular layer epitaxy apparatus according tothe present invention may preferably further include a shaft forrevolution in the form of a tubular cylinder connected to an electricwiring and a service water piping outside of the common chamber andadapted to be turned and vertically moved in a state in which saidcommon chamber means is held at vacuum, a cooling water piping disposedin a region of each of the substrate heating units and connected to theservice water piping, and a carrier plate with its center disposed incoincidence with an axis of rotation of the shaft for revolution.

This construction permits a carrier plate to turn around the axis ofrotation of the shaft for revolution continuously to allow the processesto be conducted in parallel, and prevents the cooling water piping forsupply of cooling water into the substrate heating units and theelectric wiring for power supply or a temperature monitoringthermo-couple from twisting.

Also, in a combinatorial molecular layer epitaxy apparatus according tothe present invention, the shaft for revolution has preferably attachedthereto, a slip ring adapted to vacuum seal an upper end of the shaftfor revolution and to connect that upper end electrically to theexternal electrical wiring, a cooling water sealing means for connectionto the external service water piping, and a cooling water conduit meansconnected water tight to the cooling water sealing means and having theshaft for revolution passed therethrough coaxially to permit said shaftto rotate in a sliding contact therewith.

This construction permits the carrier plate to be vertically moved androtated by means of the shaft for revolution without producing a twistof a cooling water piping or the electrical wiring.

Further, in a combinatorial molecular layer epitaxy apparatus accordingto the present invention, the cooling water conduit means may preferablycomprise an inner and an outer cooling water conduits disposed coaxiallywith the shaft for revolution and forming a single cooling waterpassage.

This construction permits supplying cooling water while holding theshaft for revolution moving vertically and rotating in its vacuum sealedstate.

Also, in a combinatorial molecular layer epitaxy apparatus according tothe present invention, a substrate heating unit may preferably include asubstrate turning mechanism for rotating the substrate holder.

This construction improves temperature uniformity over a substrate bypermitting the substrate holder to rotate.

Further, in a combinatorial molecular layer epitaxy apparatus accordingto the present invention, the substrate heating units may preferably beturnable and each include a substrate turning mechanism that provides arotation from a driving power for turning around the substrate heatingunits.

This construction permits a single driving power to be used both to turnthe substrate heating units and to rotate the substrate holder.

Also, in a combinatorial molecular layer epitaxy apparatus according tothe present invention, a substrate heating unit may preferably include asubstrate turning mechanism for rotating the substrate holder in avacuum chamber.

This construction permits a substrate heating unit and a processingchamber together to form a vacuum chamber with pressure and temperaturetherein controllable, yet permitting the substrate holder to be rotated.

Further, in a combinatorial molecular layer epitaxy apparatus accordingto the present invention, the process conducting chambers may preferablyinclude an annealing chamber for annealing substrates held by thesubstrate holder, a preheating chamber for preheating the substratesheld by the substrate holder to a given temperature in a high vacuum,and a growth chamber for forming a thin film on a said substrate held bythe substrate holder, and an etching chamber for etching a substratewith the thin film caused to grow and formed thereon.

This construction permits performing a plurality of processes inparallel consecutively.

Also, in a combinatorial molecular layer epitaxy apparatus according tothe present invention, the substrate holder may preferably be formedwith openings each in the form of a slit, arranged to surround one ormore substrates.

This construction permits reducing an escape of the amount of heat fromthe substrate, and thus allows the substrate to be heated uniformly andefficiently.

Further, in a combinatorial molecular layer epitaxy apparatus accordingto the present invention, the substrate holder may preferably be in theform of a disk that is hollow inside and having its side wall formedwith an annular groove that permits the substrate holder to be held on asubstrate heating unit.

This construction permits easily loading the substrate holder into thesubstrate heating unit.

Also, in a combinatorial molecular layer epitaxy apparatus according tothe present invention, the substrate holder may preferably comprise aholder ring having a stepped edge inside and having its side wall formedwith an annular groove that permits the substrate holder to be held on asubstrate heating unit, and a holder plate in the form of a disk to beseated on the stepped edge of the holder ring for supporting one or moresubstrate, the disk holder plate being formed of a material that is highin heat absorbing efficiency on its side facing the substrate heatingunit.

This construction that allows the holder plate heated to contact onlywith the stepped edge of the holder ring permits reducing escape of theamount of heat by heat conduction and hence improves temperatureuniformity over the holder plate.

Further, in a combinatorial molecular layer epitaxy apparatus accordingto the present invention, the holder plate formed of the material thatis high in heat absorbing efficiency may preferably be constituted by aninconel plate with a surface region oxidated at a high temperature.

This construction permits effectively heating the holder plate.

Also, in a combinatorial molecular layer epitaxy apparatus according tothe present invention, the substrate heating means comprises a lampheater, the substrate holder and the holder plate being arranged to lieat a focusing position of the lamp heater.

This construction permits heat rays focused on the substrate holder andthe holder plate to be effectively heated.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will better be understood from the followingdetailed description and the drawings attached hereto showing certainillustrative forms of embodiment of the present invention. In thisconnection, it should be noted that such forms of embodiment illustratedin the accompanying drawings hereof are intended in no way to limit thepresent invention but to facilitate an explanation and understandingthereof.

FIG. 1 is a diagrammatic view illustrating a combinatorial molecularlayer epitaxy apparatus according to a first form of embodiment of thepresent invention;

FIG. 2 is a view of appearance that illustrates a combinatorialmolecular layer epitaxy apparatus according to a second form ofembodiment of the present invention;

FIG. 3 is a view of appearance that illustrates an essential portion ofa growth chamber in a combinatorial molecular layer epitaxy apparatusaccording to the second form of embodiment of the present invention,depicting an independent vacuum chamber comprising a substrate heatingunit and a growth chamber;

FIG. 4 is a detailed cross sectional view that shows a substrate heatingunit according to the second form of embodiment of the presentinvention, depicting a state thereof in which a carrier plate has beenmoved to its lower end in pressure contact with a partition;

FIGS. 5(a) and 5(b) are a perspective view of appearance and a crosssectional view, respectively, that illustrate a substrate holder;

FIGS. 6(a) and 6(b) are a perspective view of appearance and a crosssectional view, respectively, that illustrate a modification of thatsubstrate holder;

FIGS. 7(a) and 7(b) are a perspective view of appearance and a crosssectional view, respectively, that illustrate an alternative substrateholder;

FIG. 8 is a cross sectional view that illustrates a shaft for revolutionaccording to the second form of embodiment of the present invention;

FIG. 9 is a detailed view that illustrates a pipe or conduit arrangementin the shaft for revolution according to the second form of embodimentof the present invention;

FIG. 10 is a view of appearance of an apparatus according to a thirdform of embodiment thereof of the present invention; and

FIG. 11 is a detailed view that illustrates a substrate heating unitaccording to the third form of embodiment thereof of the presentinvention.

BEST MODES FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail withreference to suitable forms of embodiment thereof illustrated in thedrawing figures. While the present invention will hereinafter been setforth with respect to certain illustrative forms of embodiments thereof,it will readily be appreciated to be obvious to a person skilled in theart that many alternations thereof, omissions therefrom and additionsthereto can be made without departing from the essences of scope of thepresent invention. Accordingly, it should be understood that theinvention is not intended to be limited to the specific forms ofembodiment thereof set forth below, but to include all possible forms ofembodiment thereof that can be made within the scope with respect to thefeatures specifically set forth in the appended claims and encompassesall the equivalents thereof.

A detailed description will first be given in respect of a first form ofembodiment of the present invention that is typical for a combinatorialmolecular layer epitaxy apparatus according thereto.

FIG. 1 is a diagrammatic view that depicts a combinatorial molecularlayer epitaxy apparatus according to the first form of embodiment of thepresent invention. While a combinatorial laser molecular beam epitaxyapparatus is illustrated in FIG. 1 to constitute a thin film growtheffecting apparatus, it can be substituted by a combinatorial gas sourceorganometallic molecular beam epitaxy apparatus.

A combinatorial molecular layer epitaxy forming apparatus according tothe present invention can be embodied as two alternative forms thatdiffer partly in configuration depending on raw materials supplied andmaterial components to be prepared, i. g., as a combinatorial lasermolecular beam epitaxy apparatus in which a raw material in solid stateis gasified by a pulsed laser beam to allow molecular layers to growepitaxially for each of the molecular layers, and which thus is suitableto combinatorially synthesize an inorganic superstructure, and acombinatorial gas source organic metal molecular beam epitaxy apparatuswhich using a raw material in a gaseous or gasified state, e. g., of anorganometallic compound, is suitable to form an metallic or organicsuperstructure by permitting molecular layers to grow epitaxially foreach of the molecular layers. The two apparatus forms may be identicalto each other but for different manners of supplying raw materials.

First, an explanation is given in respect of a combinatorial lasermolecular beam epitaxy apparatus.

Referring to FIG. 1, a combinatorial laser molecular beam epitaxyapparatus according to this form of embodiment includes a vacuum chamber2, an ultra-high vacuum pump 4 such as a turbo-molecular pump, an ionpump or a cryopump for evacuating the vacuum chamber 2 via a gate valve(not shown) to a high vacuum, a substrate holder 6 rotatable for holdinga plurality of substrates 5, and a lamp heater 8 disposed in a rear sideof the substrate holder 6 for heating the substrates.

The apparatus also includes a rotatable shaft 9 that supports thesubstrate holder 6, rotatable target tables 10 and 10 juxtaposed with oropposed to the substrate holder 6, a plurality of different solid rawmaterial targets 12 loaded on these target tables 10 and 10, lightsources 14 and 14 for excimer laser beams 13 and 13 for gasifying theseraw material targets 12, lenses 15 and 15 for focusing these laserbeams, windows 16 and 16 for introducing the laser beams into the vacuumchamber 2, an electron gun 18 for reflex high-energy electrondiffraction (hereinafter referred to as “RHEED”) analysis for impromptuor instantaneously [in the sense occurring at a particular instant]monitoring epitaxial growth of a molecular layer on a thin film formingsubstrate, and a screen 17 for RHEED analysis.

A control unit is further included but not shown, which is used tocontrol the home positions and rotational angular positions of thesubstrate holder 6 and the target tables 10 and 10. The control unit isprovided also to select particular types of targets for, and inconjunction with, a particular substrate on which growth is to beeffected, and further to control a pulse duration of the pulsedirradiating excimer laser.

The ultra-high vacuum pump 4 should desirably have a capability to keepthe vacuum chamber 2 at a pressure in the order of 10⁻¹⁰ Torr. Also, thevacuum chamber 2 is designed to have its pressure controllable byadjustment of the opening of a valve (not shown). It should further benoted that the ultra-high vacuum pump is provided with a rotary pump asan assistant pump.

A substrate 5 when lying at a position where it has a thin film growingthereon is heated by the lamp heater 8 and elsewhere it is heated by apreheating or after-heating lamp heater 7. These lamps are disposed inthe neighbourhood of the substrate holder 6. Optionally, a lamp heatermay be disposed in the substrate holder itself in which case it is madeadjustable to heat a substrate at a thin film growing position to agrowth temperature and to warm it elsewhere at a given temperature.

While in the form of embodiment shown in FIG. 1 common use is made ofthe single vacuum chamber for the purpose of effecting thin film growthand for the preheating or post-heating purpose, individually a chamberfor effecting growth of thin films on substrates and a chamber forpreheating or post-heating the substrates may be provided separately andindependently as disposed adjacent to each other.

The vacuum chamber in addition to having an atmospheric air inlet meansfor restoring to a normal pressure is associated with a gas feed systemincluding nozzles 19 for feeding oxygen, nitrogen and other reactivegases for effecting epitaxial growth of high temperature superconductorrelated oxides. In this connection, it should be noted that the gas feedsystem is only roughly depicted in FIG. 1, and normally has itsoperations controllable by mass flow meters and also controllable incooperation with the vacuum pump system.

To mention further, for the substrates use may be made of α-Al₂O₃, YSZ,MgO, SrTiO₃, LaAlO₃, NdGaO₃, YA1O₃, LaSrGaO₄, NdAlO₃, Y₂O₅, SrLaAlO₄,CaNdAlO₄, Si and compound semiconductors.

By the way, in order to detect RHEED oscillations based on a molecularlayer epitaxial growth effected, and yet to permit the molecular layerepitaxial growth to continue while monitoring the RHEED oscillations, itis extremely important to make flat the surface of a substrate on aatomic level and to identify an outermost atomic layer.

For example, as regards a perovskite oxide that is expressed by ageneral formula of ABO₃ in which an atomic layer of AO and an atomiclayer of BO₂ are repeated, which if AO, BO₂ or both AO and BO₂coexistent forms the uppermost surface makes a difference in the mode inwhich a film grows thereon.

For instance, a polished SrTiO₃ substrate has its uppermost surfacecomposed mainly of TiO₂ with a surface roughness of several nanometers.Wet etching such a SrTiO₃ (100) substrate in a HF/NH₃ buffer solution(pH=4.5) makes its surface flat on an atomic level and allows itsoutermost atomic layer to be formed by a TiO₂ layer.

A substrate with its surface made flat on an atomic level lends itselfto detection of RHEED oscillations caused by a growth of an individualmolecular layer.

Accordingly, this form of embodiment preferably uses a substrate withits surface made flat on an atomic level and with its outermost atomiclayer specified.

The target solid material can be any material whatsoever that is in asolid state for use. Such usable materials include high temperaturesuperconductors such as YBa₂Cu₃O₇, luminescent materials such as ZnO,(ZnMg)O, (ZnCd)O, dielectric or ferroelectric materials such as SrTiO₃,BaTiO₃, PZT and (SrBa)TiO₃, and colossal magnetoresistance materialssuch as (LaSr)MaO₃.

Further, use can be made of a single or multiple component oxide forsupply of each individual component.

Next, an explanation is given in respect of an operation of forming athin film with a combinatorial laser molecular beam epitaxy formingapparatus.

For example, pressure in the vacuum chamber 2 is controlled to be in theorder of 10⁻⁴ Torr, a substrate 5 is heated by the lamp heater 8 to agrowth temperature of, e. g., 850° C., and the substrate holder 6 isrotated or turned to locate the substrate 5 at a growth position. Thetarget tables 10 and 10 are rotated or turned to locate targets 12 and12 to given positions where they are opposed to the substrate. Thetargets 12 and 12 are irradiated with excimer laser beams 13 and 13, e.g., pulsed, for a given period of time.

The excimer laser beams impinging upon the targets will bring about ontheir surfaces both an abrupt build-up of heat and photo-chemicalreactions and cause raw materials to be explosively gasified, forming onthe substrate a thin film composed as aimed. Then, the RHEED analyzercapable of observing at a mirror reflection spot thereof, oscillationsthat follow a repetition of nucleus formation and flattening for eachlayer, strictly monitoring a thickness of the film self-controllable foreach individual monomolecular layer.

After epitaxial growth of a substance forming the thin film with themonomolecular layer on the substrate 5, the target tables 10 and 10 areturned to locate the other targets 12 and 12 at those given positions tocause a thin film of superstructure of another substance.

After preparing an artificial crystal or superlattice having a novellattice structure on the one given substrate, the substrate holder 6 isturned for processing of a next substrate.

If an epitaxial growth film is of a superconductor, the oxygen partialpressure in the vacuum chamber 2 of a reaction system is raised to meetwith required oxidation conditions. In this connection, it should benoted that this form of embodiment of the invention offers an extendedpressure reducibility and allows the oxygen partial pressure to becontrolled in an extended range.

Thus, a combinatorial laser molecular beam epitaxy apparatus accordingto this form of embodiment of the invention permits [multiple rawmaterials]×[multiple substrates]×[reaction parameters such astemperature, pressure and flux from gas phase] to be controlled orselected independently of one another and put together in any desiredcombination, and hence is capable of producing a group of substancesbrought together or synthesized in a single series of reactions into astructure systematically controlled.

An explanation is next given in respect of a combinatorial gas sourceorganometallic molecular beam epitaxy apparatus.

To this end, reference is made to FIG. 1 which was used to illustrate acombinatorial laser molecular beam epitaxy apparatus as above described,but has a structure much common to a gas source specie of embodiment ofthe invention as well.

Referring to FIG. 1, a combinatorial gas source organometallic molecularbeam epitaxy apparatus according to this form of embodiment includes avacuum chamber 2, and a vacuum evacuation system including an ultra-highvacuum pump 4 such as a turbo-molecular pump, an ion pump or a cryopumpfor evacuating the vacuum chamber 2 via a gate valve (not shown) to ahigh vacuum.

The apparatus also includes a substrate holder 6 rotatable for holding aplurality of substrates 5, and a lamp heater 8 disposed in a rear sideof the substrate holder 6 for heating the substrates, a rotatable shaft9 that supports the substrate holder 6 and the lamp heater 8, andnozzles 19 that apply flow controlled streams of a plurality of reactivegases as raw materials such as organometallic compounds onto asubstrate. Control of gas flows, their introductory on/off operations,and/or introductory timings may be effected ganged with control ofvacuum evacuation.

Also in the combinatorial gas source organometallic molecular beamepitaxy apparatus in which raw materials are gas source organometalliccompounds and adsorptive surface reactions are controlling, it iseffective to employ a laser beam as instantaneous observation means forinstantaneously monitoring epitaxial growth of an individual molecularlayer and thus to irradiate the layer growing with a laser beam andmonitor changes in intensity of the laser beam.

For monitoring epitaxial growth of each individual molecular layer,there may be utilized, for instance, a reflectance differentialspectroscopic method in which a linearly polarized light is used forincidence on a substrate at a right angle thereto and anisotropy of asurface structure of the layer in growth is detected fromcharacteristics of the reflected light, or a surface light absorption orsurface light interferometric method that determines changes in theintensity of the reflected light from changes in light absorption oroptical phase caused by surface adsorbed atoms or molecules.

To mention further, for the substrates use may be made of a compoundsemiconductor material composed of elements of, e. g., III to V groups,II to V groups, I to VII groups, II to IV groups and IV to VI groups inany of a variety of possible combinations. Further, in place of such acompound semiconductor, the substrates may be Si (silicon) substrates.

A combinatorial gas source organometallic molecular beam epitaxyapparatus permits monomolecular layers to grow epitaxially for each ofthe layers growing upon monitoring and hence is capable of producing agroup of substances brought together or synthesized in a single seriesof reactions into a structure systematically controlled, here again.

An explanation will next be given in respect of a combinatorialmolecular layer epitaxy apparatus of the present invention that isimplemented in a second form of embodiment thereof.

FIG. 2 is a view of appearance that illustrates a combinatorialmolecular layer epitaxy apparatus according to a second form ofembodiment of the present invention.

A combinatorial molecular epitaxy apparatus 20 that represents thesecond form of embodiment includes a common chamber 22, and a pluralityof processing chambers that include a growth chamber 24, an annealingchamber 26, a preheating chamber 28 and a substrate holder load lockingchamber 34. These chambers 22, 24, 26, 28 and 30 are each vacuumshielded or sealed individually, forming vacuum chambers evacuated to ahigh vacuum independently of one another.

In the common chamber 22, the processing chambers constituted by thegrowth chamber 24, the annealing chamber 26 and the preheating chamber28 are vacuum shielded or sealed by and on conveying with a carrierplate 38 a substrate heating unit 36 mounted thereto into each of thoseprocessing chambers 24, 26 and 28, and then locking them.

The growth chamber 24 provides a stage in which a thin film is caused togrow on a substrate, the annealing chamber 26 a stage in which asubstrate with a thin film formed is annealed, and the preheatingchamber 28 a stage in which a substrate is cleaned and preheated in ahigh vacuum atmosphere.

While the present forms of embodiment are thus shown and described toconduct three processes successively in these stages, it can be seenthat additional stages such as for conducting processes of etching anddoping a given area of the substrates. Then, five independent vacuumchambers come to be included.

Character “TMP” in FIG. 2 stands for a turbo molecular pump, typicallywith a rotary pump as an assistant pump, and by which each of theprocessing chambers is evacuated to an ultra-high vacuum, via a gatevalve unit (not shown).

Each of the vacuum chambers also has pressure therein controllable by avalve unit (not shown) with a valve opening adjustable and may beprovided with a further valve unit and a mass flow meter (not shown) topermit oxygen or dry nitrogen to be admitted in a flow adjusted.

The common chamber 22 is made to communicate with the growth chamber 24,the annealing chamber 26 and the preheating chamber 28 via openings 42,42, 42 formed in a partition 39 each of which has around it an annulargroove in which an O-ring 41 is fitted. Further, the growth chamber 24,the annealing chamber 26 and the preheating chamber 28 are each vacuumsealed or shielded and held fixed to the partition 39.

In FIG. 2 three substrate heating units 36 are shown in the commonchamber 22, each accommodated in a cylindrical housing 35 which alsoaccepts a substrate holder 48 and a chuck 45 therefor as well as a lampheater 8 of the substrate heating unit 36 (see FIG. 4).

These substrate heating units 36 are each vacuum shielded or sealed at aflanged upper end 31 of the cylindrical housing 35 to, and are carriedby, the carrier plate 38 for both rotary conveyance and verticalmovement by a shaft 43 for revolution.

The shaft for revolution 43 is made to rotate by a rotational drivemechanism 60 and to vertically move by a translational movement drivemechanism 70, both in a state in which the common chamber 22 remainsvacuum shielded or sealed.

The housing 35 has its lower end flanged 33 as well which when thecarrier plate 38 reaches its end position is placed in pressure contactwith the O-ring 41 (FIG. 4) fitted in the annular groove around theopening 42 in the partition 39 to make the housing 35 vacuum shielded orsealed in isolation from the common chamber 22. Then, the substrateheating units 36, 36 and 36 and the processing chambers constituted bythe growth chamber 24, the annealing chamber 26 and the preheatingchamber 28 are designed to be evacuated and to have pressure thereincontrolled, and to be heated to respective temperatures given,independently of one another.

As shown in FIG. 2, the substrate holder loading lock chamber 34 isattached via a gate valve 46 to the common chamber 22 and has a stockhousing 49 disposed therein which carries a plurality of substrateholders 48 each loaded with substrates 5. The substrate holder loadinglock chamber 34 is also provided with a clip member 52 that isexternally operable to transfer a substrate holder 48 out of the chamber34 into the common chamber 22 in the state in which the chamber 34 isheld at high vacuum, for reception by a chuck 45 in the substrateheating unit 48.

The growth chamber 24 is identically constructed itself to that in thecombinatorial laser molecular beam epitaxy apparatus shown in FIG. 1except that only one lamp heater is here provided therefor.

Further, it should further be noted that in a laser molecular beamepitaxy as shown in FIG. 2, a target loading lock chamber 32 is attachedvia a gate valve 47 to the growth chamber 24 and has a plate 54 disposedtherein which carries a plurality of targets 12. The target loading lockchamber 32 is associated with a clip member 56 which is externallyoperable to transfer a target 12 out of the chamber 32 onto a targetplate (not shown) in the state in which the chamber 32 is held at highvacuum.

Mention is next made of details of a growth chamber.

FIG. 3 is a view of appearance that illustrates essential portions of agrowth chamber in a combinatorial laser molecular beam epitaxyapparatus, depicting an independent vacuum chamber constructed of asubstrate heating unit and a growth chamber.

As shown in FIG. 3, a vacuum chamber 100 comprising a substrate heatingunit 36 and a growth chamber 24 is set up with the substrate heatingunit 36 brought in pressure contact with a partition (illustrationomitted). A plurality of substrates 5 is shown as held by a substrateholder 48 that is carried rotatably and mounted to a substrate holderrotational drive unit 84 (shown in FIG. 2).

The growth chamber 24 is provided therein with a rotatable target table10 disposed as opposed to the substrate holder 48, and a masking plate102 placed between the substrate holder 48 and the target table 10. Themasking plate 102 has different masking patterns formed therein, e. g.,of eight types.

While the masking plate is shown to be disk shaped, it may as analternative be in the form of a shutter with shutter plates movable fromopposite sides. Then, such a masking plate is carried so as to be bothrotatable and movable vertically up and down.

A plurality of targets of different solid raw materials are loaded onthe target table 10. The apparatus further includes a light source orlaser 14 for an excimer laser beam 13 for vaporizing a target material12, a lens 15 for focusing the laser beam, a window 16 for admitting thelaser beam into the vacuum chamber 100, an electron gun 18 for reflexhigh-energy electron diffraction (hereinafter referred to “RHEED”)analysis, and a screen 17 for RHEED.

The target table 10 and the masking table 102 are each carried so as tobe both rotatable and vertically movable up and down in the state ofholding the pressure of the growth chamber 24, and are provided withtarget table rotational and translational movement drive mechanisms andmasking plate rotational and translational movement drive mechanisms,respectively.

Use is made, especially for the masking rotational drive mechanism, of astepping motor precision driven to permit a thin film to grow with acontrolled film thickness in a preselected area.

The growth chamber 24 is also provided with an atmospheric air ornitrogen admitting system for restoring to a normal pressure, and a gassupply system for oxygen and reactive gases fed onto a substrate throughnozzles when a high temperature superconductor oxide epitaxy is to beeffected (neither system shown).

Further, the home position and the angular displacement of each of thesubstrate holder 48, the masking plate 102 and the target table 10rotated or turned is made controllable by a control unit not shown.Specifically, the control unit is made to act on their respectiverotational drive mechanisms so as to allow a particular type of targetmaterial and a particular type of masking pattern 104 to be selected fora given substrate on which and at a given position of which a thin filmis intended to grow, to allow an epitaxial growth for each individualmolecular layer to be instantaneously monitored through RHEED analysis,and to allow the duration of a pulsed irradiating excimer laser beam tobe controlled in accordance with such instantaneous monitoring.

An explanation is next given of an operation of the combinatorial lasermolecular beam epitaxy apparatus according to the second form ofembodiment described, in the process of forming a thin film on asubstrate.

With reference to FIG. 3, pressure in the vacuum chamber 100 iscontrolled to a high vacuum in the order of, e. g., 10⁻⁴ Torr. A givensubstrate 5 is positioned at a growth position by rotating the substrateholder 6, or while it is heated by the lamp heater 8 to a growthtemperature, e. g., 850° C. To correspond to this particular substrate,a particular masking pattern is selected through the masking platerotating drive mechanism. A target 12 so as to be opposed to thesubstrate at its growth position is located at a given correspondingposition by turning the target table 10, and the target 12 is thenirradiated with an excimer laser beam, e. g., pulsed, for apredetermined period of time. Post-processing processes are the same asin the first form of embodiment previously described.

The operation described above may be used to effect a givencombinatorial synthesis on a plurality of substrates with a fixedmasking pattern. If a plurality of thin films that are different incomposition are to be formed on a plurality of given areas of asubstrate or superlattices with varying laminar structures are to beprepared on a substrate, the masking plate may successively be displacedto bring different masking patterns into position to cover and uncovergiven areas on the substrate. Further, above mentioned masking ispossible by using the shutter plates to cover and uncover given areas onthe substrate.

The combinatorial laser molecular beam epitaxy apparatus according tothe present form of embodiment thus permits [multiple rawmaterials]×[multiple substrates]×[reaction parameters such astemperature, pressure and flux from gas phase] to be selected orcontrolled independently of one another and put together in any desiredcombination, and hence is capable of synthesizing or bringing together agroup of substances in a single series of reactions into a structuresystematically controlled.

Yet, it should be noted that while the growth chamber is described abovefor combinatorial laser molecular beam epitaxy, the growth chamber forgas source molecular beam epitaxy is modified to include means forapplying through a nozzle onto each substrate a gas sourceorganometallic compound in a controlled flow as the multiple rawmaterial supply means for supplying a film composing raw material onto asubstrate at a growth position in the substrate holder. Such amodification represents the construction shown and described for thefirst form of embodiment.

FIG. 4 is a detailed cross sectional view that shows a substrate heatingunit according to the second form of embodiment of the presentinvention, depicting the carrier plate having been moved to its endposition to place the substrate heating unit in contact with thepartition.

As shown in FIG. 4, the substrate heating unit 36 includes a cylindricalhousing 35 having its opposite ends flanged 31 and 33, a lamp holder 82disposed across the center line of the housing 35, and a lamp heater 8mounted on the lamp holder 82 as well as a substrate turning mechanismfor rotating the substrate holder.

The lamp heater 8 needs to be cooled to ensure its safety andtemperature control stability. To this end, the lamp heater has a watercooling pipe line 201 led from the substrate heating unit and connected,via a bulk head union 203 vacuum sealed to the carrier plate 38, to acooling water circulation piping assembly 200 disposed to encircle theshaft for revolution 43 and having cooling water supply and return pipelines 202 and 202.

For the lamp heater an electrode plug 101 is provided as vacuum sealedto the carrier plate 38. Although not shown here but will be describedlater in detail, an electric power supply wiring for the lamp heater 8,signal lines for temperature control thermo-couples and so forth for thelump heater are lead to run through the inside of the shaft forrevolution 43 and lead to its outside as vacuum sealed.

The substrate revolving mechanism includes a substrate holder rotatingmember 84 arranged outside of the lamp holder 82, and a chuck 45 mountedon the rotating member 84 for positioning the substrate holder 48 at afocal point provided by the lamp heater 8.

The substrate holder rotating member 84 includes at its upper end a gearfor rotation 83 in mesh with a gear 85 fastened to one end of a shaftfor rotation 86 which has at its other end a gear for rotation 88 inmesh with a gear for revolution 65. Further, the substrate holderrotating member is provided at its lower end with a bearing 87.

Mention is next made of a substrate holder.

FIGS. 5(a) and 5(b) illustrate a substrate holder in a perspective viewof appearance and in a cross sectional view, respectively. FIG. 5(b)also depicts an orientation of the substrate holder relative to the lampheater 8.

Referring to FIG. 5, the substrate holder shown is in the form of a diskformed with a hollow interior 311 and laterally having an annular recess310 to hold the substrate holder in the chuck 45. On a surface of thesubstrate holder at its side opposite to its hollow or bottom open sideare mounted a plurality of substrates 5. The hollow and bottom openinterior is provided to have a suitable depth such as to allow thesubstrates to be effectively heated and yet to an extent sufficient toprevent deformation of the substrate holder. Further, while substratesare shown mounted as plural in number, it should be noted that only onesubstrate may be mounted. If a plurality of substrates are mounted, itis preferred that they be arranged along a circle or circles on the disksurface around its center.

Such a substrate holder with a moderately hollow interior preventsdeformation of its body portion, yet permitting effective heating ofsubstrates.

FIGS. 6(a) and 6(b) illustrate a substrate holder that represent amodification of the substrate holder of FIGS. 5(a) and 5(b), in aperspective view of appearance and in a cross sectional view,respectively. FIG. 6(b) also shows the lamp heater 8.

As shown in FIGS. 6(a) and 6(b), a modified substrate holder 308 isformed with a plurality of openings 309 in the form of slits arranged soas to surround a disk's central area in which a substrate 5 is placed.With such a substrate holder 308, a substrate 5 is heated by focusingheat rays emitted by the lamp heater 8 on an substrate holder surfacearea on which the substrate 5 is supported. While the substrate isheated by heat conduction in a portion of the substrate holder definedby the slit openings 309, presence of these openings 309 is found toreduce escape away from that portion of heat conducted. Further, itshould be noted that substrates need not be singular but may be plural.If a plurality of substrates are mounted, slit openings 309 may beformed either just to surround, or around, them.

Such a substrate holder 308 permits one or more substrates to be heatedeffectively and increases evenness of heating temperature.

FIGS. 7(a) and 7(b) shows an alternative form of the substrate holdersdescribed above, in a perspective view of appearance and in a crosssectional view, respectively. FIG. 7(b) also depict an orientation ofthe alternative substrate holder relative to the lamp heater 8.

Referring to FIGS. 7(a) and 7(b), the alternative substrate holder 48includes a holder ring 320 having its outer peripheral wall formed withan annular recess 310 for holding the substrate holder in a chuck 45 andits inner peripheral wall ending with an inner stepped edge or shoulderportion on which a holder plate 330 is seated inside of the holder ring320 and in contact with an extremely limited area.

Such a substrate holder 48 when attached to the chuck 45 is so orientedas to place the holder place 330 at a focal area of heat rays emitted bythe lamp heater. It should be noted further that the holder plate 330may be formed on its side wall with minute projections 315 havingrounded ends so it can be fitted snugly in the holder ring 320.

Also, the holder plate 330 is advantageously formed of a material thatis high in heat absorbing efficiency. Further, an oxidated or oxidematerial is formed on the disk surface facing the lamp heater 8 tomaximize the heat absorbing efficiency of the holder plate 330. Forexample, if the lamp heater is constituted by an infrared heater, it isdesirable that the holder plate be formed of -inconel and then have itssurface oxidated at a high temperature around 1000° C. to form an oxide313 colored in black so it has a maximum heat absorbing efficiency.

A substrate holder so constructed allows its holder plate to be heatedby a lamp heater at a maximum heat efficiency and minimizes escape fromthe peripheral area of the holder plate of heat conducted. Accordingly,it has the effect of rendering the holder plate temperature uniform.

An explanation is next given in detail in respect of a rotational drivemechanism for rotating the carrier plate and a translational movementdrive mechanism for translationally moving the carrier plate vertically.

Referring to FIG. 2, a rotational drive mechanism 60 for rotating thecarrier plate 38 is shown to include a motor 61 mounted on atranslational movement plate 72, a shaft 62 for transmission of adriving power of the motor 61, and a drive gear 64 attached to an endportion of the shaft 62. The drive gear 64 is in mesh with the gear forrevolution 65 provided for the revolution shaft for transmission of therotational driving power thereto.

It should be noted further that the rotational shaft 62 is made to passthrough the inside of a flexible tube 82 included to provide a vacuumshield between the movement table 72 and the growth chamber 22.

Referring to FIGS. 2 and 4, the shaft for revolution 43 has at its endportion a support member 92 fixed thereto that fixes the carrier plate38 thereto by means of a plurality of holder shafts 91. And, the gearfor revolution 65 is coupled to the support member 92 to be rotatablerelative thereto at a given torque via a bearing 93.

Referring to FIG. 2, the translational movement drive mechanism 70includes a bracket 73 secured to an upper cover or top 71 of the commonchamber 22, a rotary shaft 75 coupled to a motor 74 so as to berotationally driven thereby, and the translational movement plate 72 tobe moved translationally in vertical directions as the rotary shaft 75is rotated. The shaft for revolution 42 extends through the inside of aflexible tube 83 included to provide a vacuum shield or seal between thetranslational movement plate 72 and the growth chamber 22, ismagnetically shielded by a magnetic shielding unit 77 mounted on thetranslational movement plate 72, and is rotatably supported thereby. Themagnetic shielding unit here is provided to vacuum shield the shaft forrevolution by means of a magnetofluid.

Next, mention is made of an operation, first of the translationalmovement drive mechanism.

Referring to FIGS. 2 and 4, when the translational movement plate 72 isplaced at an upper starting position, the rotary shaft 75 is rotated bythe motor 74 to cause the plate 72 to descend. Then, the flexible tubes82 and 83 are going to shrink. As the plate 72 descends, the shaft forrevolution 43 will descend. And, a continued descent of the shaft forrevolution 43 will bring the flange 33 of the substrate heating unit 36attached to the conveying plate 38 into pressure contact with the O-ring41, the substrate heating unit thus coming to a halt.

Thus, each of the vacuum chambers is vacuum shielded or sealed to thesubstrate heating unit 36, then permitting them to be independentlyevacuated and pressure controlled, and to be each heated to a giventemperature.

An explanation is next given in respect of operations of the conveyingplate and the substrate revolving drive mechanism.

Referring to FIGS. 2 and 4, when the translational movement plate 72lies at its upper starting position, a rotational driving power providedby the motor 61 is transmitted to the shaft 62 to rotate the drive gear64. The drive gear 64 when rotated rotates the gear for revolution 65and in turn the shaft for revolution 43, causing the carrier plate torotate and thereby revolving the substrate heating unit 36. Then, thegrear for rotation 88 is caused to rotate, transmitting rotational drivevia the rotary shaft 86 to the rotary gear 83 to turn the substrateholder rotating member 85 and thus to rotate the substrate holder 48. Itshould be noted in this conneciton that each of the shaft for revolution43, the rotary shaft 62 and the rotary shaft 86 are caused to rotate inthe state in which each is vacuum shielded or sealed in its respectivevacuum chamber.

Therefore, not only is it possible to convey the substrate heating unitat the carrier plate to any given one of the vacuum chambers but it isalso possible to rotate the substrate holder 48.

When the carrier plate 38 have been translationally moved to its lowerend position with the substrate heating unit held vacuum shielded inisolation from the common chamber, the substrate heating unit locked inpressure contact with the O-ring (hence the shaft for revolution heldfrom descending further and thus locked) permits the gear for revolution65 with rotational driving power transmitted from the rotary shaft 62 tobe rotated relative to the shaft for revolution via the bearing 93 andto rotate the gear for rotation 88 and in turn the substrate holderrotating member 85, thereby rotating the substrate holder 48.

Consequently, the substrate holder can be brought into rotation in anyone of the vacuum chambers.

An explanation is next given in respect of the shaft for revolution.

FIG. 8 illustrates in a cross sectional view the shaft for revolutionfor use in the second form of embodiment of the present invention.

Referring to FIG. 8, the shaft for revolution 43 passes through a centerof the combinatorial molecular layer epitaxy apparatus 20 according tothe second form of embodiment, and extends across the common chamber ata vacuum and an outside thereof under an atmospheric pressure.

The shaft for revolution 43 has its upper end tight sealed with a slipring 301 for vacuum shielding or sealing. Electrical wires led throughthe inside of the shaft for revolution are connected to a joint of theslip ring 301 that is attached to the shaft for revolution and axialmovement therewith in sliding contact with its upper fixed takeout partensure electrical connection.

Thus, using a slip ring allows the electrical wires led through theinside of the shaft for revolution to be connected through slidingcontact to an external electrical system, even if the shaft forrevolution is rotated and axially moved.

Hence no twisting of electrical wires accompanies even with such a shaftas is rotated and axially moved.

FIG. 9 illustrates details of the shaft for revolution in the secondform of embodiment including fluid passages for cooling a lamp heater.

Referring to FIG. 9, the shaft for revolution 43 is provided with aninner and an outer cooling water conduits 401 and 403 coaxially. Coolingwater is introduced from a cooling water inlet port 402 of a coolingwater sealing unit 405 into the inner cooling water conduit 401. Thecooling water is flowing out through an outlet port 404 in an endportion of the shaft for revolution 43 and then past the cooling waterfluid passages of the lamp heater 201 and 202 (FIG. 2) is returnedthrough a return inlet port 406. The return water is passed through theouter conduit 403 and discharged through a drain port 408 of a coolingwater sealing unit 408. Further, it should be noted that the coolingwater sealing units 405 and 407 are joined together and secured to thebracket (FIG. 3). The cooling water sealing units 405 and 407 are sealedwater-tight with O-rings 409.

Consequently, a rotation of these conduits carried on the shaft forrevolution accompanies no twisting of cooling water conduits.

An explanation is next given in respect of an operation in a process byan apparatus of the second form of embodiment of the invention. Itshould be noted that for the growth chamber an example is taken of alaser molecular beam epitaxy system, and specific conditions indicatedare only for illustration.

Under a given pressure and at the room temperature, the carrier plate 38is placed at its upper starting position, and a first substrate holder48 is loaded into the chuck 45. Then, the carrier plate 38 is lowered tobring the respective substrate heating units 36 into pressure contactwith their corresponding O-rings 41 and bring them to a halt. Thepreheating chamber 28 is held at a high vacuum, e. g., at 10⁻⁶ Torr inwhich cleaning is performed, and the temperature is raised at a rate of10° C./minute up to 950° C.

On lapse of a given period of time, while the temperature of each of thesubstrate heating units is held unvaried, the common chamber and each ofthe vacuum chambers are returned to a given pressure, and the carrierplate 38 is moved to its upper starting position. Then, the carrierplate 38 is rotated to convey the substrate heating unit 36 loaded withthe first substrate holder 48 to a position above the growth chamber 24.In this stage, a second substrate holder 48 with substrates to beprocessed next is or has been loaded into the chuck 45 of anothersubstrate heater unit 36 which corresponds to the preheating chamber 28at the room temperature, namely of that substrate heating unit 36 withthe lamp heater 8 turned off.

The carrier plate 38 is then lowered to isolate the vacuum chambers fromone another. The growth chamber 24 is evacuated, and held at a highvacuum, e.g., at 10⁻⁴ Torr, and heated and held heated at a temperatureof 950° C., in which state a laser molecular beam epitaxial growth isaccomplished therein. In this stage, the preheating chamber 28 ismaintained at a high vacuum of 10⁻⁶ Torr and heated to raise itstemperature at a rate of 10° C./minute up to 950° C.

In the growth chamber 24, molecular layer epitaxial growth forindividual monomolecular layers may be effected to form a superstructureor superlattice successively on each of the substrates by permitting thesubstrate holder to be rotated. Thereafter, each of the vacuum chambersand the common chamber 22 are returned to a given pressure while the settemperature of 950° C. is maintained. Then, the carrier plate 38 areagain moved to its upper starting position, and its rotation follows toconvey the substrate heating unit 36 loaded with the first substrateholder 48 to a position above the annealing chamber 26. In this stage, athird substrate holder 48 is or has been loaded into the chuck 45 of thesubstrate heating unit 36 that corresponds to the preheating chamber 28.

The carrier plate 38 is then lowered again to isolate the vacuumchambers from one another. The annealing chamber 28 is reduced inpressure, and held at a pressure of, e. g., at 1 Torr, and cooled from atemperature of, e. g., from 950° C. at a cooling rate of 10° C./minutefor a given period of time for annealing. In the annealing chambercontrol is effected to make the oxygen partial pressure optimum. Afterthe lamp heater 8 is turned off to bring the annealing chamber at a roomtemperature, each of the vacuum chambers and the common chamber 22 areturned to a given pressure while leaving the other substrate heatingunits 36 and 36 at 950° C. In this state, the carrier plate 38 is movedto its upper starting position and is then rotated to return to its homeposition. The substrate holder with the substrates each with theepitaxial growth is removed and transferred into the stock housing 49.Then, the chuck 45 of the substrate heating unit 36 is loaded with anew, fourth substrate holder loaded with substrates to be processed.

Thus, the above described form of embodiment of the invention as well,permits [multiple raw materials]×[multiple substrates]×[reactionparameters such as temperature, pressure and flux from gas phase] to beselected or controlled independently of one another and put together inany desired combination, and hence is capable of synthesizing orbringing together in a single series of reactions a group of substancesinto a structure systematically controlled.

Moreover, an arrangement is provided in which the growth chamber 24 forforming monomolecular epitaxial growth layers on substrates, theannealing chamber 28 for annealing the thin film growth formed onsubstrates and the cleaning chamber 28 for preliminarily cleaningsubstrates are associated respectively with corresponding heating units36, 36 and 36, and that has rendered pressure and temperaturescontrollable individually for each of the chamber/unit pairs, thusindependently one pair from another. Consequently, it is made possibleto convey substrates without the need for cooling or temperaturereduction and to carry out the successive processes consecutively orwithout interruption.

An explanation is next given of a third form of embodiment of thepresent invention.

FIG. 10 illustrates the third form of embodiment in its appearance view.

In the third form of embodiment, the invention employs a construction inwhich heating units are arranged not on a circle but in a row, and soare arranged vacuum chambers corresponding to the heating units. Yet, itshould be noted that the substrate holder loading lock chamber and so onare omitted.

As shown in FIG. 10, a combinatorial molecular layer epitaxy apparatusaccording to the third form of embodiment 400 includes a common chamber422 in which substrate heating units 436 are conveyed into theirrespective processing chambers constituted by a preheating chamber 410,a growth chamber 412, an etching chamber 414 and an annealing chamber416 and locked therewith, respectively. Each of the process chambers arethereby vacuum shielded or sealed to form an independent vacuum chamberthat permits independent evacuation to a given high vacuum.

The common chamber 422 is designed to communicate with the preheatingchamber 410, the growth chamber 412, the etching chamber 414 and theannealing chamber 413 through their respective openings 42 formed in apartition 439 each of which has an O-ring fitted in an annular grooveformed around it. Further, each of the chambers is vacuum sealed to thepartition 439 and securely held thereby.

The substrate heating units 436 is carried by a carrier plate 438adapted to be moved vertically by vertically movable shafts 401 and 401and are supported, e. g., on a chain conveyer, to move along a loopedpath 402 formed in the carrier plate 438. It should be noted furtherthat a motor 429 is provided to convey the substrate heating units 436along the looped chain conveyer path 402, and a motors 421 are alsoprovided to rotate the substrate holders retained in the substrateheater units 436, respectively.

FIG. 11 illustrates in somewhat detailed view a substrate heating unitin the third form of embodiment of the invention, in which the samereference characters as used in FIG. 2 represent parts or componentswhich are common to those in the second form of embodiment.

Referring to FIG. 11, the substrate heating unit in the third form ofembodiment 436 is carried by the carrier plate 438 by means of a shaft406 and is provided with a rotational drive mechanism for rotating thesubstrate holder in a configuration as shown in FIG. 2. The motor 421for applying a rotational driving power to the rotary shaft 86 iscarried on a top or upper cover 418.

Mention is next given of an operation of the third form of embodiment.

The carrier plate 438 is lowered to bring the flange 33 of the substrateheating unit 436 in pressure contact with the O-ring on the partition.The O-ring compressed causes the substrate heating unit to come to ahalt. In this stage, each of the vacuum chambers is or has been vacuumsealed, individually evacuated to a given vacuum with pressurecontrolled and heated or has been heated to a given temperature,independently of one another.

Subsequently, the carrier plate 438 is caused to ascend and to come to ahalt at its upper starting position, permitting the substrate heatingunits to move horizontally for positioning above their respective vacuumchambers. In movement of the substrate heating units, the substrateholder is rotated and a given temperature is held therefor.

This arrangement here again permits each of the vacuum chamber to bevacuum shielded or sealed to its heating counterpart, individuallyevacuated to a given vacuum with pressure controlled and heated to agiven temperature, independently of one another.

It should be noted in connection with the above that the growth chambermay have a construction as in the first or second form of embodiment.

Industrial Applicability

As will be apparent from the foregoing description, a combinatorialmolecular layer epitaxy apparatus according to the present invention isextremely useful as a monomolecular layer epitaxy apparatus to make anefficient search for a material or substance efficiently in a shortperiod of time.

What is claimed is:
 1. A combinatorial molecular layer epitaxy apparatuscomprising: a common chamber having pressure therein controllable; oneor more conveyable substrate heating units having a substrate holder forholding one or more substrates in the common chamber; and a plurality ofprocess conducting chambers having pressure therein controllable andprovided to correspond to the substrate heating units, said processconducting chambers including a growth chamber which has a multiple rawmaterial supply means for supplying raw materials onto a said substrateheld by a said substrate heating unit, a gas supply means for feeding agas onto a surface of the substrate, and an instantaneous observationmeans for instantaneously observing epitaxial growth of monomolecularlayers for each of the layers on the substrate surface, therebypermitting growth temperature, pressure and supply of the raw materialsto be controlled for each of the substrates and producing a group ofsubstances caused each to grow epitaxially in an individualmonomolecular layer and brought together for each of the substrates,systematically in accordance with indications of the instantaneousobservation means.
 2. A combinatorial molecular layer epitaxial growthapparatus as set forth in claim 1, wherein said multiple raw materialsupply means includes a laser molecular beam epitaxy means forvaporizing with an excimer laser beam a plurality of targets ofdifferent solid raw materials and for forming a thin film of acomposition as aimed on each of the substrates.
 3. A combinatorialmolecular layer epitaxial growth apparatus as set forth in claim 1,wherein said multiple raw material supply means includes a lasermolecular beam epitaxy means and said substrates is composed of amaterial selected from the group which consists of α-Al₂O₃, YSZ, MgO,SrTiO₃, LaAlO₃, NdGaO₃, YAlO₃, LaSrGaO₄, Y₂O₅, SrLaAlO₄, CaNdAlO₄, Siand compound semiconductors.
 4. A combinatorial molecular layerepitaxial growth apparatus as set forth in claim 1 or claim 2, whereinsaid multiple raw material supply means includes a laser molecular beamepitaxy means, and the target solid raw materials include substancesadapted to form a material selected from the group which consists of ahigh temperature superconductor, a luminescent material, a dielectricmaterial, a ferroelectric material, colossal magnetoresistance materialand an oxide material.
 5. A combinatorial molecular layer epitaxyapparatus as set forth in any one of claims 1 to 3, wherein saidmultiple raw material supply means includes a target turn tablesupported to be rotatable and vertically movable for carrying targets,and a masking plate means disposed between said targets and saidsubstrates and supported to be rotatable and vertically movable.
 6. Acombinatorial molecular layer epitaxy apparatus as set forth in claim 5,wherein said masking plate means includes a plurality of masking plateshaving different masking configurations which are exchangeable insuccession while epitaxial growths are effected.
 7. A combinatorialmolecular layer epitaxy apparatus as set forth in claim 5, wherein saidmasking plate means comprises a mask movable horizontally with respectto said substrates and is adapted to cover and uncover either or both ofa said substrate and a given area thereof with said movable mask.
 8. Acombinatorial molecular layer epitaxy apparatus as set forth in claim 1,wherein said multiple raw material supply means includes a lasermolecular beam epitaxy means, and said instantaneous observation meanscomprises a reflex high-energy electron beam diffraction analysis means.9. A combinatorial molecular layer epitaxy apparatus as set forth inclaim 1, wherein the apparatus further includes a target loading lockchamber for loading said growth chamber with targets therein.
 10. Acombinatorial molecular layer epitaxy apparatus as set forth in claim 1,wherein said multiple raw material supply means includes a gas sourcemolecular beam epitaxy means adapted to spray and thereby to supply aflow controlled stream of a gaseous organometallic compound through anozzle means onto each of said substrates.
 11. A combinatorial molecularlayer epitaxy apparatus as set forth in claim 1, wherein said multipleraw material supply means includes a gas source molecular beam epitaxymeans, and said instantaneous observation means comprises an opticalmeans that makes observation based on any of reflectance differentialspectroscopic, surface light absorbing and surface light interferometricprocesses.
 12. A combinatorial molecular layer epitaxy apparatus as setforth in any one of claims 1, 10 or 11, wherein said multiple rawmaterial supply means includes a gas source molecular beam epitaxymeans, and said substrates comprise substrates composed of Si or acompound semiconductor.
 13. A combinatorial molecular layer epitaxyapparatus as set forth in claim 1, wherein said substrates comprise asubstrate whose surface is made flat on an atomic level and whoseoutermost atomic layer is identified.
 14. A combinatorial molecularlayer epitaxy apparatus as set forth in claim 1, wherein said commonchamber is provided with a substrate holder loading lock chamber forexchanging the substrate holders in a state in which a high vacuum isheld therefor.
 15. A combinatorial molecular layer epitaxy apparatus asset forth in claim 1, wherein a said substrate heating unit is adaptedto contact with its corresponding process conducting chamber to vacuumseal the same, said substrate heating unit and process conductingchamber then forming an independently pressure controllable vacuumchamber.
 16. A combinatorial molecular layer epitaxy apparatus as setforth in claim 1, wherein said substrate heating units are jointlyadapted to be turned around and vertically moved by a carrier plate soas to be conveyed into association with said process conducting chambersin succession.
 17. A combinatorial molecular layer epitaxy apparatus asset forth in claim 1, wherein the apparatus further includes a shaft forrevolution in the form of a tubular cylinder connected to an electricwiring and a service water piping outside of said common chamber andadapted to be turned and vertically moved in a state in which saidcommon chamber means is held at vacuum, connecting a cooling waterpiping disposed in a region of each of said substrate heating units withconnected to said service water piping, and a carrier plate with itscenter disposed in coincidence with an axis of rotation of said shaftfor revolution.
 18. A combinatorial molecular layer epitaxy apparatus asset forth in claim 17, wherein said shaft for revolution has attachedthereto, a slip ring adapted to vacuum seal an upper end of said shaftfor revolution and to connect said upper end electrically to saidexternal electrical wiring, a cooling water sealing means for connectionto said external service water piping, and a cooling water conduit meansconnected water tight to said cooling water sealing means and havingsaid shaft for revolution passed therethrough coaxially to permit saidshaft to rotate in a sliding contact therewith.
 19. A combinatorialmolecular layer epitaxy apparatus as set forth in claim 17 or 18,wherein said cooling water conduit means comprises an inner and an outercooling water conduit disposed coaxially with said shaft for revolutionand forming a single water passage.
 20. A combinatorial molecular layerepitaxy apparatus as set forth in any one of claims 1 or 15 to 17,wherein said substrate heating units includes a substrate turningmechanism for rotating said substrate holder.
 21. A combinatorialmolecular layer epitaxy apparatus as set forth in any one of claims 1 or15 to 17, wherein said substrate heating units are turnable and eachincludes a substrate turning mechanism that provides a rotation from adriving power for revolving said substrate heating units.
 22. Acombinatorial molecular layer epitaxy apparatus as set forth in any oneof claims 1 or 15 to 18, wherein a said substrate heating unit includesa substrate turning mechanism for rotating said substrate holder in asaid vacuum chamber.
 23. A combinatorial molecular layer epitaxyapparatus as set forth in claim 1, wherein said process conductingchambers include an annealing chamber for annealing substrates held by asaid substrate holder, a preheating chamber for preheating thesubstrates held by said substrate holder to a given temperature in ahigh vacuum, and a growth chamber for forming a thin film on a saidsubstrate held by said substrate holder, and an etching chamber foretching said substrate with the thin film caused to grow and formedthereon.
 24. A combinatorial molecular layer epitaxy apparatus as setforth in any one of claims 1 or 14, wherein a said substrate holder isformed with openings each in the form of a slit, arranged to surroundone or more substrates.
 25. A combinatorial molecular layer epitaxyapparatus as set forth in any one of claims 1 or 14, wherein a saidsubstrate holder is in the form of a disk that is hollow inside andhaving its side wall formed with an annular groove that permits saidsubstrate holder to be held on a said substrate heating unit.
 26. Acombinatorial molecular layer epitaxy apparatus as set forth in any oneof claims 1 or 14, wherein said substrate holder comprises a holder ringhaving a stepped edge inside and having its side wall formed with anannular groove that permits said substrate holder to be held on a saidsubstrate heating unit, and a holder plate in the form of a disk to beseated on the stepped edge of said holder ring for supporting one ormore substrate on its side facing said substrate heating unit, said diskholder plate being formed of a material that is high in heat absorbingefficiency.
 27. A combinatorial molecular layer epitaxy apparatus as setforth in claim 26, wherein said holder plate formed of said materialthat is high in heat absorbing efficiency is constituted by an inconelplate with a surface region oxidated at a high temperature.
 28. Acombinatorial molecular layer epitaxy apparatus as set forth in any oneof claims 1 or 15 to 17, wherein said substrate heating means comprisesa lamp heater.
 29. A combinatorial molecular layer epitaxy apparatus asset forth in claims 26, wherein said substrate holder is arranged to lieat a focusing position of the lamp heater.
 30. A combinatorial molecularlayer epitaxy apparatus as set forth in claim 26, wherein said holderplate is arranged to lie at a focusing position of the lamp heaterconstituting said substrate heating unit.